Scraper for rock bit cutter



Dec. 19, 1961 F. D. KINNEAR 3,013,621

SCRAPER FOR ROCK BIT CUTTER Filed July 8, 1958 INVENTOR Few/v D. film 5,4?

0W A W ATTORNEY United States This invention relates to earth boring drills of the type which comprises a conical shaped cutter arranged to roll along the bottom of the hole to dislodge particles of rock therefrom by a chipping or crushing action, and also a circulating mud system for carrying the chips or particles of detritus to the surface of the hole. In such drills, the mud, with the entrained chips or cuttings, is deposited as a layer on the heel of the cone cutter. The action is cumulative until the mud, along with the chips of rock and other abrasive particles, rubs against the adjacent side wall of the bit head and the abrasive particles cut or score the wall. This action tends to wear away the wall of the head in the region where it supports the cutter, and occasionally results in the escape of roller bearings from the cutter, or the loss of the cutter from the bit head.

In order to remove such abrasive particles from the heel of the cutter, it has been proposed to provide a pad of wear resistant material on the confronting wall of the bit head, the pad being secured to the wall by mounting it within a groove extending substantially radially along the wall. In its usual commercial form, the surface of the pad lies flush with the surface of the bit head wall and thus acts to disintegrate the abrasive particles as they come in contact with the walls. Usually, the wear resistant material is of the tube metal type and comprises a combination of tungsten carbide in a steel matrix. While the pad arrangement has met with some success, it has the disadvantage in that it increases the cost of manufacture of a rock bit, not only because of the cost of the substantial quantities of materials in the pad but also because of the special machining operations required for milling the groove in the wall of the bit head.

The general object of this invention is to provide a more effective and more economical means for removing abrasive particles from the heel of a conical cutter.

More specifically, it is an object of this invention to eliminate the need for a groove in the bit head wall; to reduce the quantity of hard metal required; to replace the usual pad with a device having greater wear resistance; and to provide an arrangement which can be manufactured more quickly.

In accordance with the above objects, the present invention provides a scraper comprising tungsten carbide particles applied superficially to a smooth fiat surface on the bit head wall and secured to said surface as an overlay by the sweat-on process.

Still another object is to enable the scraper to extend a substantial distance away from the plane surface of the bit head wall without requiring increased quantities of expensive materials, without weakening the support for the scraper, and without interference with the action of roller bearings which revolve in an annular path overlapping that of the scraper.

Other objects and features of this invention will appear more clearly from the following description and accompanying drawings. In said drawings:

FIG. 1 is a side elevation of the lower end of a bit head segment embodying this invention, showing in broken lines the associated cutter, roller bearings and ball bearings;

FIG. 2 is a fragmentary cross section taken on the atet 3,013,621 Patented Dec. 19, 1961 ice FIG. 3 is a fragmentary cross section,greatly enlarged,

taken on the line 3-3 of FIG. 2;

FIG. 4 is a fragmentary cross section of the bit head wall in the same plane and on the same scale as FIG. 3, but in the process of sweating on the hard metal.

Referring to FIG. 1, the bit head segment 8 has an upper portion (not shown) of the usual construction, and has a depending portion 9 provided with an inner wall 10 which inclines downwardly and outwardly with respect to the axis of rotation of the bit head. The wall It cooperates with the diverging walls of two complementary bit head segments (not shown) to define a recess 11 for the reception of three conical cutters 12 (one shown). Near its lower end the wall 10 is provided with an unbroken, flat, annular surface 13. Extending downwardly and inwardly from the fiat annular surface 13, and coaxial therewith, is a spindle 14 having a cylindrical raceway 15 for the reception of roller bearings 16, the roller bearings being arranged to cooperate with the spindle to support the cutter 12. The cutter has a heel face 17 lying in a plane in spaced parallel relation to the fiat annular surface 13. The rollers are spaced from the surface 13 by means of a boss 18 having a flat annular :face 19 abutting against the outer ends of the rollers, along the inner portions of the rollers. The boss 18, the wall surface 13 and the spindle 14 are all integral parts of the bit head segment 8, and are made of steel.

The heel 17 of the cuttercollects drilling mud which enters the space between the heel 17 and the wall surface 13 and tends to build up on the heel until the mud, together with abrasive particles or cuttings deposited with the mud, runs along with the cutter heel and tends to rub against the bit head wall 10 at the surface 13. The action of such abrasive materials in collecting on the cone and in scoring the Wall of the bit head is progressive and if not controlled, might wear away part of the wall surface 13 and permit the rollers to escape or the cutter to become detached from the spindle.

In order to prevent the abrasive particles or cuttings from collecting on the cutter heel to the extent that they may damage the bit head wall, the present invention provides a novel form of scraper attached to the wall and arranged to scrape the mud and chips from the heel 17 and thereby remove the abrasive particles from the cutter before they can cause damage.

The scraper 21 is generally of rectangular shape as shown in FIG. 2, and is preferably inclined with respect to the radius of spindle 14. The inner end of the scraper is relatively close to the axis of the spindle and lies within the outermost radius of the annular path of the rollers 16. At its outer end the scraper 21 extends to the peripheral edge of the flat annular surface 13 and runs around the edge along the front face of the bit head portion 9 to cover the lateral area 22 (FIG. 1). Contrary to prior arrangements, the scraper 21 of this invention is not in the form of an insert mounted in a groove in the bit head wall, but is in the form of an overlay applied superficially to the flat surface 13. Referring to FIG. 4, the scraper 21, when in the process of manufacture, consists of particles of tungsten carbide 23 supported on the smooth flat surface 13 and held in place by a binder of sodium silicate. The tungsten carbide particles are then permanently sweated on to the surface 14 by applying heat from a suitable torch 24. The torch, which may be of the oxy-acetylene type as shown, or of the atomic hydrogen type, provides a reducing flame in order to avoid oxidation. The primary purpose of the sodium silicate is to act as an adhesive to hold the tungsten carbide in place until the welder can apply heat to fuse the carbide particles 23 to the steel. Sufiicient heat is then applied to bring only the surface of the steel to slightly fused condition to wet the tungsten carbide particles. The latter will then be partly embodied in the steel and surface tension will build the steel partly up around the carbides 23. In the final structure as shown in FIG. 3, the tungsten carbide par ticles extend away from the plane of surface 13 and as far as a plane indicated by the broken line 25. The scraper becomes effective just as soon as the chips or abrasive particles in the mud, which accumulate on the cutter heel 17, each the plane 25 of the exposed face of the scraper, which in practice is spaced from the plane of heel surface 17 by about one-fiftieth of an inch (.020). The exposed portions of the scraper which engage the abrasive laden mud on the cutter heel consist of a high concentration of tungsten carbide and therefore are more abrasion resistant and have a longer life as compared with the usual scraper of the prior art composed of a mixture of tungsten carbide particles in a steel matrix. A further advantage of the present scraper over those of the prior art is that it is less expensive to manufacture because of the absence of any machining operation for forming a groove in the bit head to receive the scraper, and also because it requires less of the expensive tungsten carbide particles when applied superficially in the form of a layer than in prior commercial structures where such materials extend below the surface of the bit head wall and fill a groove or recess below the surface. As seen in FIGS. 2 and 3, the rollers 16 are in partial alinement at their inner portions with the boss 18 and at their outer portions with the scraper 21. The rollers 16 are shielded from contact with the scraper by means of the shoulder 19 which is offset from the surface 13 by a distance considerably greater than the thickness of the scraper 21.

What is claimed is:

1. In a well drill, a bit head having a downwardly extending leg, a spindle integral with the leg and projecting downwardly and inwardly therefrom, the inner wall of the leg having a flat annular surface surrounding the spindle in a plane at right angles to the axis of the spindle, a rotary cutter mounted on the spindle having a heel surface in spaced parallel relation to the flat surface of the bit head, and a scraper attached to said flat surface for removing abrasive accumulated mud particles from the heel surface of the cutter, the scraper comprising particles of hard material applied superficially to a narrow strip area of said fiat surface and sweated thereon as an overlay, the said inner wall being provided with an annular boss thereon, the periphery of the boss having the same diameter as the inside diameter of the said flat surface and the free end of the boss defining an annular shoulder in a plane parallel to said fiat surface, the spindle having a plurality of cylindrical rollers supporting the heel portion of the cutter, each of said rollers being arranged in one position to register partly with the shoulder and partly with the scraper, and the plane of the shoulder being axially spaced from the fiat annular surface by a distance greater than the thickness of the scraper, whereby to shield the rollers from contact with the scraper.

2. In an earth boring bit head including a depending leg having a flat inner wall, a spindle integral with the latter and extending at right angles therefrom, a rotary cone cutter upon the spindle having a flat heel surface in parallel spaced relation to the said inner wall, and cylindrical roller bearings rotatively supporting the cone cutter upon the spindle, a scraper comprising hard particles, the individual particles of which being partly embedded in the surface of the said inner wall and partly projecting therefrom and the projecting parts of the particles being in spaced relation to the heel surface of the cone cutter, an annular boss projecting integrally from the said inner wall defining a flat shoulder around the base of the spindle parallel to the heel surface of the cone cutter, the roller bearings having an outer coplanar set of end faces, the said end faces at all times in part underlying the flat shoulder and at all times in part underlying the particles of the scraper, and the boss having an axial dimension substantially beyond the projecting parts of the said particles whereby the said end faces of the roller bearings underlying the particles of the scraper are maintained in a predetermined spaced relation to the said particles.

References Cited in the file of this patent UNITED STATES PATENTS 

